preamp active filters - Page 3

clem_o · 6th April 2006, 11:12 AM

Hi Andrew,

And despite that, we manage to blow up countless numbers at the Uni...

Cheers!!

Clem

DD_Davo · 6th April 2006, 11:17 AM

aha right, ive moved the wire from pin 3 to the rail above i.e so it isnt really connected to anything. However i've still the same problem, adding a 9v battery doesnt have any effect. Infact i can unplug the opamp from the board (remove it) and theres no difference the audio signal is fed through and sounds slightly different as though its passively altered. hmmm i must have done something majorly wrong here

(ive 3 741's so hopefully i wont kill them all, and yes ive had them go up in smoke before but luckily no fire

)

DD_Davo · 6th April 2006, 11:55 AM

ok following this:

Ive rebuilt the circuit as shown in the attached image the problem now, like ive incurred before is that theres loads of noise introduced into the circuit and the audio single is very crackly. This worsens when i power the opamp from a 9v battery. This should be simple too!

richie00boy · 6th April 2006, 11:58 AM

Quote:

Originally posted by DD_Davo
aha right, ive moved the wire from pin 3 to the rail above i.e so it isnt really connected to anything.

No, not connected to anything is not what clem said. Connect it to ground. Read his post again, he even drew a simple wiring didagram for you and explained it clearly. ALL your grounds are wrong.

In fact you are lucky your power amp has a DC blocking cap at the input or your would have blown up your speakers.

In future I would also recommend you breadboard with +ve at the top and -ve at the bottom to make it easier to follow. And put chips so that the pins are like 1234, not backwards. But I see you have done this now with your last pic.

DD_Davo · 6th April 2006, 12:04 PM

yes i realised and i have done what he said but now theres the problem of introduced noise. I still cant understand the fact that powering the opamp makes no difference, i must have done something stupidly wrong since theres no amplifcation whatso ever to match the gain on the input.

Ok its de-amplyfying, by large amounts, some of the noise is from a poorly soldered 3.5mm connection so im sorting that but that unfortunately isn't going to solve the filter problem.. hmmm

clem_o · 6th April 2006, 12:51 PM

Hi DD_Davo,

If you haven't solved it in 12 hours I'll see if i can put something together and take a pic of it.

Cheers!!

Clem

ps: why 12 hours - sleep time here...

Hang on - one question: when you write "...a 9V battery..." you mean TWO 9V batteries, right? If not, well, there's the problem...

richie00boy · 6th April 2006, 01:27 PM

The schematic is also wrong, for bass boost. Everything except the 1k input resistor should be in the feedback loop.

DD_Davo · 6th April 2006, 05:25 PM

nope! a singular 9v battery, i was told it would work...
but thanks for your help everybody you'll be glad to know it works a treat now!

thanks again

richie00boy · 6th April 2006, 06:34 PM

You can make it work off a single battery, but not like you have arranged it.

clem_o · 7th April 2006, 01:23 AM

Congratulations! Enjoy!

Cheers

Clem

6th April 2006, 01:27 PM	#27
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	The schematic is also wrong, for bass boost. Everything except the 1k input resistor should be in the feedback loop. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

6th April 2006, 06:34 PM	#29
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	You can make it work off a single battery, but not like you have arranged it. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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6th April 2006, 11:12 AM	#21
clem_o diyAudio Member Join Date: Jun 2005 Location: Manila	Hi Andrew, And despite that, we manage to blow up countless numbers at the Uni... Cheers!! Clem

6th April 2006, 11:17 AM	#22
DD_Davo diyAudio Member Join Date: Aug 2004 Location: England South Yorkshire	aha right, ive moved the wire from pin 3 to the rail above i.e so it isnt really connected to anything. However i've still the same problem, adding a 9v battery doesnt have any effect. Infact i can unplug the opamp from the board (remove it) and theres no difference the audio signal is fed through and sounds slightly different as though its passively altered. hmmm i must have done something majorly wrong here (ive 3 741's so hopefully i wont kill them all, and yes ive had them go up in smoke before but luckily no fire )

6th April 2006, 12:04 PM	#25
DD_Davo diyAudio Member Join Date: Aug 2004 Location: England South Yorkshire	yes i realised and i have done what he said but now theres the problem of introduced noise. I still cant understand the fact that powering the opamp makes no difference, i must have done something stupidly wrong since theres no amplifcation whatso ever to match the gain on the input. Ok its de-amplyfying, by large amounts, some of the noise is from a poorly soldered 3.5mm connection so im sorting that but that unfortunately isn't going to solve the filter problem.. hmmm

6th April 2006, 12:51 PM	#26
clem_o diyAudio Member Join Date: Jun 2005 Location: Manila	Hi DD_Davo, If you haven't solved it in 12 hours I'll see if i can put something together and take a pic of it. Cheers!! Clem ps: why 12 hours - sleep time here... Hang on - one question: when you write "...a 9V battery..." you mean TWO 9V batteries, right? If not, well, there's the problem...

6th April 2006, 05:25 PM	#28
DD_Davo diyAudio Member Join Date: Aug 2004 Location: England South Yorkshire	nope! a singular 9v battery, i was told it would work... but thanks for your help everybody you'll be glad to know it works a treat now! thanks again

7th April 2006, 01:23 AM	#30
clem_o diyAudio Member Join Date: Jun 2005 Location: Manila	Congratulations! Enjoy! Cheers Clem

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